Semiconductor device and method of forming wafer level ground plane and power ring

ABSTRACT

A semiconductor die has active circuits formed on its active surface. Contact pads are formed on the active surface of the semiconductor die and coupled to the active circuits. A die extension region is formed around a periphery of the semiconductor die. Conductive THVs are formed in the die extension region. A wafer level conductive plane or ring is formed on a center area of the active surface. The conductive plane or ring is connected to a first contact pad to provide a first power supply potential to the active circuits, and is electrically connected to a first conductive THV. A conductive ring is formed partially around a perimeter of the conductive plane or ring and connected to a second contact pad for providing a second power supply potential to the active circuits. The conductive ring is electrically connected to a second THV.

CLAIM OF DOMESTIC PRIORITY

The present application is a continuation of U.S. patent applicationSer. No. 12/905,797, filed Oct. 15, 2010, now U.S. Pat. No. 8,097,943,which is a continuation of U.S. application Ser. No. 11/951,729, filedDec. 6, 2007, now U.S. Pat. No. 7,838,395.

FIELD OF THE INVENTION

The present invention relates in general to semiconductor devices and,more particularly, to a semiconductor device having wafer level groundplane or ring and power ring.

BACKGROUND OF THE INVENTION

Semiconductor devices are found in many products in the fields ofentertainment, communications, networks, computers, and householdmarkets. Semiconductor devices are also found in military, aviation,automotive, industrial controllers, and office equipment. Thesemiconductor devices perform a variety of electrical functionsnecessary for each of these applications.

The manufacture of semiconductor devices involves formation of a waferhaving a plurality of die. Each semiconductor die contains hundreds orthousands of transistors and other active and passive devices performinga variety of electrical functions. For a given wafer, each die from thewafer typically performs the same electrical function. Front-endmanufacturing generally refers to formation of the semiconductor deviceson the wafer. The finished wafer has an active side containing thetransistors and other active and passive components. Back-endmanufacturing refers to cutting or singulating the finished wafer intothe individual die and then packaging the die for structural support andenvironmental isolation.

One goal of semiconductor manufacturing is to produce a package suitablefor faster, reliable, smaller, and higher-density integrated circuits(IC) at lower cost. Flip chip packages or wafer level chips scalepackages (WLCSP) are ideally suited for ICs demanding high speed, highdensity, and greater pin count. Flip chip style packaging involvesmounting the active side of the die facedown toward a chip carriersubstrate or printed circuit board (PCB). The electrical and mechanicalinterconnect between the active devices on the die and conduction trackson the carrier substrate is achieved through a solder bump structurecomprising a large number of conductive solder bumps or balls. Thesolder bumps are formed by a reflow process applied to solder materialdeposited on contact pads which are disposed on the semiconductorsubstrate. The solder bumps are then soldered to the carrier substrate.The flip chip semiconductor package provides a short electricalconduction path from the active devices on the die to the carriersubstrate in order to reduce signal propagation length, lowercapacitance, and achieve overall better circuit performance.

In many applications, it is desirable to optimize power and groundreturn paths to reduce parasitic capacitance. Some semiconductorpackages have used power rings and ground rings to shorten the power andground return paths. However, in WLCSP, space constraints make the useof power and ground rings difficult.

SUMMARY OF THE INVENTION

In one embodiment, the present invention is a method of making asemiconductor device including the steps of providing a semiconductordie with a plurality of contact pads, forming a die extension regionaround a periphery of the semiconductor die, forming a plurality ofconductive vias in the die extension region around the periphery of thesemiconductor die, forming a conductive plane on a center area of thesemiconductor die and connected to a first one of the plurality ofcontact pads and a first one of the plurality of conductive vias at alevel of the plurality of contact pads, forming a conductive ringpartially around a perimeter of the conductive plane and connected to asecond one of the plurality of contact pads and a second one of theplurality of conductive vias, and singulating the semiconductor devicethrough the plurality of conductive vias.

In another embodiment, the present invention is a method of making asemiconductor device including the steps of providing a semiconductordie having an active surface, depositing a molding compound around aperiphery of the semiconductor die to form a die extension region thatcovers sidewalls of the semiconductor die, forming a plurality ofconductive vias in the die extension region, forming a conductive planeover the active surface of the semiconductor die to connect to a firstcontact pad on the active surface and a first one of the plurality ofconductive vias, and forming a conductive ring partially around aperimeter of the conductive plane to connect to a second contact pad onthe active surface and a second one of the plurality of conductive vias.

In another embodiment, the present invention is a method of making asemiconductor device including the steps of providing a semiconductordie, forming a die extension region around a periphery of thesemiconductor die that covers sidewalls of the semiconductor die,forming a conductive plane over the semiconductor die to connect to thesemiconductor die and a first conductive via in the die extensionregion, and forming a conductive ring partially around a perimeter ofthe conductive plane to connect to the semiconductor die and a secondconductive via in the die extension region.

In another embodiment, the present invention is a semiconductor deviceincluding a semiconductor die. A die extension region is formed around aperiphery of the semiconductor die and covers sidewalls of thesemiconductor die. A conductive plane is formed over the semiconductordie to connect the semiconductor die to a first conductive via in thedie extension region. A conductive ring is formed partially around aperimeter of the conductive plane to connect the semiconductor die and asecond conductive via in the die extension region.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flip chip semiconductor device with solder bumps providingelectrical interconnect between an active area of the die and a chipcarrier substrate;

FIGS. 2a-2e illustrate a process of forming a ground plane or ring andpower ring connected to THVs around a periphery of the die;

FIG. 3 illustrates an orthogonal view of the ground plane or ring andpower ring connected to THVs around a periphery of the die;

FIGS. 4a-4b illustrate the ground plane or ring and power ring formed ona passivation layer and connected to THVs around a periphery of the die;

FIGS. 5a-5c illustrate the ground plane or ring and power ring connectedto full via THVs around a periphery of the die; and

FIG. 6 illustrate the ground plane or ring connected to topsideinterconnects.

DETAILED DESCRIPTION OF THE DRAWINGS

The present invention is described in one or more embodiments in thefollowing description with reference to the Figures, in which likenumerals represent the same or similar elements. While the invention isdescribed in terms of the best mode for achieving the invention'sobjectives, it will be appreciated by those skilled in the art that itis intended to cover alternatives, modifications, and equivalents as maybe included within the spirit and scope of the invention as defined bythe appended claims and their equivalents as supported by the followingdisclosure and drawings.

The manufacture of semiconductor devices involves formation of a waferhaving a plurality of die. Each die contains hundreds or thousands oftransistors and other active and passive devices performing one or moreelectrical functions. For a given wafer, each die from the wafertypically performs the same electrical function. Front-end manufacturinggenerally refers to formation of the semiconductor devices on the wafer.The finished wafer has an active side containing the transistors andother active and passive components. Back-end manufacturing refers tocutting or singulating the finished wafer into the individual die andthen packaging the die for structural support and/or environmentalisolation.

A semiconductor wafer generally includes an active surface havingsemiconductor devices disposed thereon, and a backside surface formedwith bulk semiconductor material, e.g., silicon. The active side surfacecontains a plurality of semiconductor die. The active surface is formedby a variety of semiconductor processes, including layering, patterning,doping, and heat treatment. In the layering process, semiconductormaterials are grown or deposited on the substrate by techniquesinvolving thermal oxidation, nitridation, chemical vapor deposition,evaporation, and sputtering. Photolithography involves the masking ofareas of the surface and etching away undesired material to formspecific structures. The doping process injects concentrations of dopantmaterial by thermal diffusion or ion implantation.

Flip chip semiconductor packages and wafer level packages (WLP) arecommonly used with integrated circuits (ICs) demanding high speed, highdensity, and greater pin count. Flip chip style semiconductor device 10involves mounting an active area 12 of die 14 facedown toward a chipcarrier substrate or printed circuit board (PCB) 16, as shown in FIG. 1.Active area 12 contains active and passive devices, conductive layers,and dielectric layers according to the electrical design of the die. Theelectrical and mechanical interconnect is achieved through a solder bumpstructure 20 comprising a large number of individual conductive solderbumps or balls 22. The solder bumps are formed on bump pads orinterconnect sites 24, which are disposed on active area 12. The bumppads 24 connect to the active circuits by conduction tracks in activearea 12. The solder bumps 22 are electrically and mechanically connectedto contact pads or interconnect sites 26 on carrier substrate 16 by asolder reflow process. The flip chip semiconductor device provides ashort electrical conduction path from the active devices on die 14 toconduction tracks on carrier substrate 16 in order to reduce signalpropagation, lower capacitance, and achieve overall better circuitperformance.

FIGS. 2a-2e illustrate a process of forming THVs on a periphery of asemiconductor die in a wafer level chip scale package (WLCSP). The THVsare formed through a non-conductive passivation or polymer die extensionregion. In one process of forming THVs, the semiconductor die are formedon a semiconductor wafer using conventional integrated circuitprocesses, as described above. The semiconductor wafer is diced toseparate the semiconductor die into individual units. The semiconductordie are then transferred onto a temporary chip carrier.

FIG. 2a shows coverlay tape 30 disposed between ends of chip carrier 32.Semiconductor die 36 is transferred and affixed to coverlay tape 30using die attach material with its active surface and contact pads 38oriented face down onto the tape. Likewise, semiconductor die 42 istransferred and affixed to coverlay tape 30 using die attach materialwith its active surface and contact pads 44 oriented face down onto thetape. Semiconductor die 36 and 42 can also be mounted to coverlay tape30 using post wafer saw tape transfer.

In FIG. 2b , a polymer molding compound 50 is deposited around aperiphery of semiconductor die 36 and 42 down to coverlay tape 30. Thepolymer molding compound 50 forms a non-conductive die extension regionaround a periphery of semiconductor die 36 and 42. The coverlay tape isthen peeled away to expose the contact pads and active front side ofsemiconductor die 36 and 42.

In FIG. 2c , the semiconductor die are inverted such that the contactpads and active front side of semiconductor die 36 and 42 face upward.THVs 52 are formed in the die extension region between semiconductor die36 and 42 by etching, laser drilling, or other conventional method. Anelectrically conductive material is deposited in THVs 52 using anevaporation, electrolytic plating, electroless plating, or screenprinting process. The conductive material can be aluminum (Al), copper(Cu), tin (Sn), nickel (Ni), gold (Au), or silver (Ag). A redistributionlayer (RDL) 54 is formed between THVs 52 and the respective contact pads38 and 44 of semiconductor die 36 and 42. RDLs 54 can be made with Al,aluminum copper alloy (AlCu), Cu, or Cu alloy. RDLs 54 operate as anintermediate conduction layer to route electrical signals between THVs52 and contact pads 38 and 44. A passivation layer 57 is formed overRDLs 54, contact pads 38 and 44, and semiconductor die 36 and 42 forstructural support and physical isolation. Passivation layer 57 can bemade with silicon dioxide (SiO2), silicon oxynitride (SiON), siliconnitride (SixNy), polyimide (PI), benzocyclobutene (BCB), polybenzoxazole(PBO), or other insulating material.

A ground plane or ring 55 is formed on an active surface ofsemiconductor die 36 and 42. A power ring 56 is formed around groundplane or ring 55 on semiconductor die 36 and 42. Ground plane or ring 55and power ring 56 can be made with Al, AlCu, Cu, or Cu alloy anddeposited using an evaporation, electrolytic plating, electrolessplating, or screen printing process. In another embodiment, plane orring 55 is used for the power connection and ring 56 is used for theground connection. A passivation layer 57 is formed over RDLs 54,contact pads 38, power ring 56, ground plane or ring 55, andsemiconductor die 36 and 42 for structural support and physicalisolation. Passivation layer 57 can be made with SiO2, SiON, SixNy, PI,BCB, PBO, or other insulating material.

In FIG. 2d , RDLs 58 are formed on a backside of the semiconductor die,opposite the active front side of the die, and electrically contact thebackside of THVs 52. RDLs 54 can be made with Al, AlCu, Cu, or Cu alloy.An under bump metallization (UBM) 60 is deposited and patterned toelectrically contact RDLs 58. In one embodiment, UBMs 60 may include awetting layer, barrier layer, and adhesive layer. RDLs 58 operate as anintermediate conduction layer to route electrical signals between THVs52 and UBMs 60. A passivation layer 62 is formed over RDLs 58 andtransfer molding compound 50 for structural support and physicalisolation. Passivation layer 62 can be made with SiO2, SiON, SixNy, PI,BCB, PBO, or other insulating material.

An electrically conductive solder material is deposited over UBMs 60through an evaporation, electrolytic plating, electroless plating, balldrop, or screen printing process. The solder material can be any metalor electrically conductive material, e.g., Sn, lead (Pb), Ni, Au, Ag,Cu, bismuthinite (Bi) and alloys thereof, or mixtures of otherelectrically conductive material. In one embodiment, the solder materialis 63 percent weight of Sn and 37 percent weight of Pb. The soldermaterial is reflowed by heating the conductive material above itsmelting point to form spherical balls or bumps 66. In one embodiment,solder bumps 66 are about 75 μm in height. In some applications, solderbumps 66 are reflowed a second time to improve electrical contact toUBMs 60. UBMs 60 and solder bumps 66 represent one type of interconnectstructure.

Semiconductor die 36 and 42 are singulated along the die extensionregion. The die extension region is cut by a cutting tool such as a sawor laser. The cutting tool completely severs the die extension region toseparate the die.

FIG. 2e illustrates semiconductor die 36 following singulation of thedie extension region through a center area of THVs 52. Eachsemiconductor die has a similar final configuration. Contact pads 38electrically connect through RDLs 54, THVs 52, RDLs 58, and UBMs 60 tosolder bumps 66, as shown in FIG. 2e . Ground plane or ring 55 and powerring 56 also connect through RDLs 54 to THVs 52.

Further detail of the ground plane or ring 55 and power ring 56 is shownin FIG. 3. Semiconductor die 36 has contact pads 38 formed on its activesurface. RDLs 54 electrically connect contact pads 38 to THVs 52.Depending on the electrical interconnect of the active circuits, some ofthe contact pads 38 are electrically isolated from adjacent THVs 52,i.e., no connecting RDL is formed. Ground plane or ring 55 connectsthrough RDLs 54 to THVs 52, which in turn connect through RDLs 58 andUBMs 60 to solder bumps 66. Likewise, power ring 56 connects throughRDLs 54 to THVs 52, which in turn connect through RDLs 58 and UBMs 60 tosolder bumps 66. The wafer level ground plane or ring 55 and power ring56 provide shorter power and return path through THVs. The shorter pathleads to less parasitic capacitance and enhanced electrical performanceof the WLCSP package.

In FIGS. 4a-4b , semiconductor die 70 has contact pads 72 formed on itsactive surface. RDLs 74 electrically connect contact pads 72 to THVs 76.Depending on the electrical interconnect of the active circuits, some ofthe contact pads 72 are electrically isolated from adjacent THVs 76,i.e., no connecting RDL is formed. THVs 76 are formed in moldingcompound 80 which operates as the die extension region as described inFIGS. 2a-2e . In this embodiment, molding compound 80 is formed withsufficient width to contain THVs 76 (full vias) and THVs 82 (half vias).

A ground plane or ring 84 is formed on an active surface ofsemiconductor die 70. A power ring 86 is formed around ground plane orring 84 on semiconductor die 36. Ground plane or ring 84 and power ring86 can be made with Al, AlCu, Cu, or Cu alloy and deposited using anevaporation, electrolytic plating, electroless plating, or screenprinting process. In another embodiment, plane or ring 84 is used forthe power connection and ring 86 is used for the ground connection. Apassivation layer 88 is formed over RDLs 74, contact pads 72, power ring86, ground plane or ring 84, and semiconductor die 70 for structuralsupport and physical isolation. Passivation layer 88 can be made withSiO2, SiON, SixNy, PI, BCB, PBO, or other insulating material.

RDLs 90 are formed on a backside of the semiconductor die, opposite theactive front side of the die, and electrically contact the backside ofTHVs 76. RDLs 90 can be made with Al, AlCu, Cu, or Cu alloy. A UBM 92 isdeposited and patterned to electrically contact RDLs 90. In oneembodiment, UBMs 92 may include a wetting layer, barrier layer, andadhesive layer. RDLs 90 operate as an intermediate conduction layer toroute electrical signals between THVs 76 and UBMs 92. A passivationlayer 94 is formed over RDLs 90, semiconductor die 70, and moldingcompound 80 for structural support and physical isolation. Passivationlayer 94 can be made with SiO2, SiON, SixNy, PI, BCB, PBO, or otherinsulating material.

An electrically conductive solder material is deposited over UBMs 92through an evaporation, electrolytic plating, electroless plating, balldrop, or screen printing process. The solder material can be any metalor electrically conductive material, e.g., Sn, Pb, Ni, Au, Ag, Cu, Biand alloys thereof, or mixtures of other electrically conductivematerial. The solder material is reflowed by heating the conductivematerial above its melting point to form spherical balls or bumps 96. Insome applications, solder bumps 96 are reflowed a second time to improveelectrical contact to UBMs 92. UBMs 92 and solder bumps 96 represent onetype of interconnect structure.

Ground plane or ring 84 connects through RDLs 74 to THVs 76 or 82, whichin turn connect through RDLs 90 and UBMs 92 to solder bumps 96.Likewise, power ring 86 connects through RDLs 74 to THVs 76 or 82, whichin turn connect through RDLs 90 and UBMs 92 to solder bumps 96. Thewafer level ground plane or ring 84 and power ring 86 provide shorterpower and return path through THVs. The shorter path leads to lessparasitic capacitance and enhanced electrical performance of the WLCSPpackage.

In FIGS. 5a-5b , semiconductor die 100 has contact pads 102 formed onits active surface. RDLs 104 electrically connect contact pads 102 toTHVs 106. Depending on the electrical interconnect of the activecircuits, some of the contact pads 102 are electrically isolated fromadjacent THVs 106, i.e., no connecting RDL is formed. THVs 106 areformed in molding compound 108 which operates as the die extensionregion as described in FIGS. 2a-2d . In this embodiment, moldingcompound 108 is formed with sufficient width to contain THVs 106 (fullvias).

A ground plane or ring 110 is formed on an active surface ofsemiconductor die 100. A power ring 112 is formed around ground plane orring 110 on semiconductor die 100. Ground plane or ring 110 and powerring 112 can be made with Al, AlCu, Cu, or Cu alloy and deposited usingan evaporation, electrolytic plating, electroless plating, or screenprinting process. In another embodiment, plane or ring 110 is used forthe power connection and ring 112 is used for the ground connection. Apassivation layer 114 is formed over RDLs 104, contact pads 102, powerring 112, ground plane or ring 110, and semiconductor die 100 forstructural support and physical isolation. Passivation layer 114 can bemade with SiO2, SiON, SixNy, PI, BCB, PBO, or other insulating material.A plurality of semiconductor die can be stacked and interconnectedthrough THVs 106, as shown in FIG. 5 c.

In FIG. 6, semiconductor die 120 has contact pads 122 formed on itsactive surface. RDLs 124 electrically connect contact pads 122 to THVs126. Depending on the electrical interconnect of the active circuits,some of the contact pads 122 are electrically isolated from adjacentTHVs 126, i.e., no connecting RDL is formed. THVs 126 are formed inmolding compound 130 which operates as the die extension region asdescribed in FIGS. 2a-2e . In this embodiment, molding compound 80 isformed with sufficient width to contain THVs 126 (half vias) and otherTHVs (full vias).

RDLs 140 are formed on a backside of the semiconductor die, opposite theactive front side of the die, and electrically contact the backside ofTHVs 126. RDLs 140 can be made with Al, AlCu, Cu, or Cu alloy. A UBM 142is deposited and patterned to electrically contact RDLs 140. In oneembodiment, UBMs 142 may include a wetting layer, barrier layer, andadhesive layer. RDLs 140 operate as an intermediate conduction layer toroute electrical signals between THVs 126 and UBMs 142. A passivationlayer 144 is formed over RDLs 140, semiconductor die 120, and moldingcompound 130 for structural support and physical isolation. Passivationlayer 144 can be made with SiO2, SiON, SixNy, PI, BCB, PBO, or otherinsulating material.

An electrically conductive solder material is deposited over UBMs 142through an evaporation, electrolytic plating, electroless plating, balldrop, or screen printing process. The solder material can be any metalor electrically conductive material, e.g., Sn, Pb, Ni, Au, Ag, Cu, Biand alloys thereof, or mixtures of other electrically conductivematerial. The solder material is reflowed by heating the conductivematerial above its melting point to form spherical balls or bumps 146.In some applications, solder bumps 146 are reflowed a second time toimprove electrical contact to UBMs 142. UBMs 142 and solder bumps 146represent one type of interconnect structure.

A ground plane or ring 150 is formed over insulating layer 152, whichcan be part of molding compound 130 or a passivation layer. Apassivation layer 154 is formed over RDL 124. UBM 156 connects to RDL124. Solder bump 158 is formed on UBM 156. UBM 164 connects to groundplane or ring 150. Solder bump 166 is formed on UBM 164. Solder bump 166can also be used as a heat sink.

While one or more embodiments of the present invention have beenillustrated in detail, the skilled artisan will appreciate thatmodifications and adaptations to those embodiments may be made withoutdeparting from the scope of the present invention as set forth in thefollowing claims.

What is claimed:
 1. A method of making a semiconductor device,comprising: providing a semiconductor die; depositing an encapsulantaround a peripheral area of the semiconductor die to form a dieextension region; forming a plurality of conductive vias through theencapsulant in the die extension region; forming a conductive plane overthe semiconductor die and electrically connected to a first one of theconductive vias; and forming a conductive ring over the semiconductordie and electrically connected to a second one of the conductive vias.2. The method of claim 1, further including coupling the conductiveplane and conductive ring to the conductive vias.
 3. The method of claim1, further including forming the conductive plane over an active surfaceof the semiconductor die.
 4. The method of claim 1, further includingcoupling the conductive plane or conductive ring to a contact pad of thesemiconductor die.
 5. A semiconductor device, comprising: asemiconductor die; an encapsulant deposited around a peripheral area ofthe semiconductor die to form a die extension region; a first conductivevia disposed through the encapsulant in the die extension region; aconductive plane formed over the semiconductor die and coupled to thefirst conductive via; a second conductive via disposed through theencapsulant in the die extension region; and a conductive ring formedover the semiconductor die and coupled to the second conductive via. 6.The semiconductor device of claim 5, further including: a conductivelayer formed over the semiconductor die; and a plurality of bumps formedover the conductive layer.
 7. The semiconductor device of claim 5,further including an insulation layer formed between the semiconductordie and the conductive plane.
 8. The semiconductor device of claim 5,wherein the conductive plane provides a first power supply potential tothe semiconductor die and the conductive ring provides a second powersupply potential to the semiconductor die.
 9. The semiconductor deviceof claim 5, wherein the conductive plane is formed over an activesurface of the semiconductor die.
 10. The semiconductor device of claim5, further including a heat sink disposed over the conductive plane. 11.A method of making a semiconductor device, comprising: providing asemiconductor die; depositing a molding compound in a die extensionregion around a peripheral area outside a footprint of the semiconductordie; forming a first conductive via and second conductive via throughthe molding compound in the die extension region; forming a conductiveplane over the semiconductor die and electrically connected to thesemiconductor die and first conductive via; and forming a conductivering over the semiconductor die and electrically connected to thesemiconductor die and second conductive via.
 12. The method of claim 11,further including forming a first conductive layer over thesemiconductor die.
 13. The method of claim 11, further including forminga conductive layer over the semiconductor die opposite the conductiveplane.
 14. The method of claim 11, wherein the conductive plane providesa first power supply potential to the semiconductor die and theconductive ring provides a second power supply potential to thesemiconductor die.
 15. The method of claim 11, further including formingthe conductive plane over an active surface of the semiconductor die.16. A method of making a semiconductor device, comprising: providing asemiconductor die; depositing a molding compound in a peripheral regionof the semiconductor die to form a die extension region; forming aplurality of conductive vias in the die extension region; forming aconductive plane over an active surface of the semiconductor die toconnect to a first contact pad on the active surface and a firstconductive via of the plurality of conductive vias; and forming aconductive ring partially around a perimeter of the conductive plane toconnect to a second contact pad on the active surface and a secondconductive via of the plurality of conductive vias, wherein thesemiconductor device includes a wafer level chip scale package.
 17. Themethod of claim 16, further including forming a conductive layer over asurface of the semiconductor die opposite the active surface and inelectrical contact with the plurality of conductive vias.
 18. The methodof claim 16, further including forming the plurality of conductive viasinto a first row of conductive vias and a second row of conductive viasoffset from the first row of conductive vias.
 19. The method of claim16, wherein the conductive plane provides a first power supply potentialto the semiconductor die and the conductive ring provides a second powersupply potential to the semiconductor die.
 20. The method of claim 16,further including: forming an under bump metallization over theconductive plane; and forming a bump on the under bump metallization.21. The method of claim 16, wherein the conductive plane is formed overa center area of the active surface of the semiconductor die.